paper 2 things i need to remember Flashcards
FORMATION OF AMINE:
1-bromoethane + ammonia–>
2-bromopentane + ammonia–>
further substitution of haloalkanes to amines can cause a secondary or tertiary amine, hence why we need excess ammonia to stop this. write the equation for:
bromoethane + ethylamine–>
what is an alpha amino acid?
amino acid with carboxyl + amine groups on same carbon
what are delocalised pi electrons?
electrons shared over more than 2 carbons
why can cyclohexene react with bromine without HCC but not benzene?
1) cyclohexene pi electrons are localised, in benzene they are delocalised
2) cyclohexene has a greater pi electron density
3) cyclohexene is more able to polarise electrophiles
why is phenol more reactive than benzene?
1) the lone electron pair on the oxygen on phenol is delocalised into the pi ring
2) phenol has a greater pi electron density
3) phenol is more able to polarise electrophiles
why is nitrobenzene less reactive than benzene
1) -NO2 group is electron-withdrawing
2) electron density of pi cloud decreases
3) less able to polarise electrophiles
test for phenol + observations
add Br2 water, white ppt forms + Br2 water decolourises
draw products of phenol + HNO3 (nitration)
2-nitrophenol/ 4-nitrophenol + H2O
activating/ electron-donating groups (2,4-directing)
-OH + -NH2 (increase pi electron density)
deactiviting/ electron-withdrawing groups (3,5- directing)
-NO2 (decreases pi electron density)
how to identify specific carbonyls
add 2,4-DNP, recrystallise + filter orange ppt, test melting point + compare to a database
why do nucleophiles react with carbonyls?
C=O bond is polar bc oxygen is more electronegative, carbon is electron-deficient + nucleophiles are attracted to electron-deficient atoms
why are carboxylic acids soluble in water?
they can form hydrogen bonds with water due to having the O-H bond
order of reactivity with carboxylic acids, acyl chlorides, acid anhydrides
acyl chlorides (Cl very electronegative so C more elctron-deficient)> acid anhydrides> carboxylic acids
reaction of acyl chloride to carboxylic acid + observations
RCOCl + H2O –> RCOOH + HCl (violent reaction, steamy fumes of HCl formed)
what is nmr + how does it work?
nuclear magnetic resonance: a nucleus has 2 different spin states with different energies- with correct radio frequency, nuce.us can absorb energy + flip between these states (resonance), allowing identification of specific chemical environments
what is TMS used as?
STANDARD to show frequencies of different absorptions
why are deuterium-containing compounds e.g/ CDCl3 used as solvents?
deuterium doesn’t show up on NMR spectrum bc of even number of particles in its nucleus
definition of condensation polymerisation
joining of 2 monomers in a condensation reaction, removing a small molecule usually water
what are biodegradable polymers?
broken down by microorganisms into water, CO2 + other biological molecules
what are photodegradable polymers?
contains bonds that are weakened when light is adsorbed to start degredation e.g. C=O
what is a sigma bond?
head-on overlap of orbitals directly in a line between bonded atoms
limitations of TLC
compounds often have similar Rf values, + unknown compounds have no Rf value for reference
stationary + mobile phases of TLC
s: silica
m: solvent
separates by relative adsorption
stationary + mobile phases of GC
s: high boiling point liquid
m: inert carrier gas
separates by relative solubility
limitations of GC
same as TLC + not all substances will be separated
method of purifying organic liquid with separating funnel
1) pour impure mixture into separating funnel, allow to settle (lower density layer on top), open tap + run off aqueous layer
2) add NaCO3 to organic layer to remove acidic impurities.
3) swirl funnel + invert, occasionally opening tap to remove evolved CO2
4) open tap + separate 2 layers + repeat washings of organic layer
5) run organic layer into conical flask + add drying agent e.g. CaCl2 to remove water from organic liquid, til it’s clear
6) decant organic liquid from drying agent + distil, then collect distillate at boiling point of pure liquid
method of purification of organic solid by recrystallisation
1) dissolve impure solid in minimum volume of hot solvent, ensuring max recrystallisation
2) cool solution with ice bath, recrystallising organic compound bc insoluble in cold solvent
3) filter under reduced pressure
4) wash solid with cold solvent
5) dry
melting point determination of pure solid method
1) seal one end of capillary tube by rotating over hot Bunsen
2) allow to cool and fill about 5mm depth of solid
3) place tube + thermometer into melting point apparatus
4) heat solid slowly, ensuring accurate value, + record temp when solid melts.
5) compare mp value with databook
